Hunting cabin heating question

Here are the specs first. I just built a cabin. 2-story, and each floor is 384 sqft. I have solar panels and three 210 reserve capacity deep cycle marine batteries.
I want to install a propane heater/furnace. But.... It must run on 12vdc, or VERY LOW AMP DRAW 110 vac.
I'm thinking a 35,000 btu RV furnace, but I'm curious what ideas others may have.
I only have solar for power, so that limits the game.
Suggest away, and please be specific, or offer your services if you know how to install.

Having living in remote alaska for yrs u have a few options but I would go with a drip heater they require no power and will easily heat that space. They run on fuel oil its a fool proof system. plus being fuel oil they heat with a dry heat give off no water vapor like a propain or natural gas set up. The best part is zero power required so if your solar fails you still have heat. The system works just like an old school oil lamp sucks up fuel threw a wic system. I have one in one of my remote cabins its 2 story 25 ft by 25 ft and it will cook you out of that place at 50 below zero. Other nice thing they work great for doing chili or stews on top of them and are completely silent.

The empire is a great way to go.I have a friend who lives in a 20 X 30 slab on grade ,1 story cabin. The Empire keeps the whole place warm all through winter. He does have a wood burner too but that will roast you out. New ones are over a thousand, used anywhere from 300 to 700.Some of them have the blower but my friends doesnt.The heater is also in a back room that is a combo bath and utility because the plumbing is mounted outside the walls so there is little chance of the pipes freezing.He has left the house all winter with it on a low setting and every time I went to check on it the place was fine.He also does not have power. We wired the place for 12 volt and 120V on the lighting. 2 bulb fixture one side 12V one side 120V on the other. He uses 2 deep cycle batteries in rotation. he leaves one outside on a solar charger till the other one goes dead. all the rest is wired for 120V for that we wired a plug outside for a generator that goes to the electrical panel.

We use a freestanding LP fireplace in our cabin. It has a pipe thru the wall with an outside vent similar to a built in gas fireplace. The fireplace doesnt have a fan so it doesn't use electricity. We use a ceiling fan to distribute the heat when we are there and shut the unit off when leaving. It does have a wall thermostat.

384 Sq ft is roughly a 20x20 cabin, nice sized for a hunting shack. About twice the size of my 10x20 fishouse. The heat will naturally rise, so not sure if there is a big need for a motorhome type unit that is forced air. Those units need power to operate the fan and furnace both. I don't belive the furnace will operate with dead batteries.

Given that, I would go with an Empire 35k BTU wall unit. It is a direct vent out the wall unit. Not sure if you are just using this in the fall, or in the winter too.

My 10x20 Fishhouse uses an Empire 18k BTU unit, and it keeps up on Lake of the Woods except down to about -35 below zero with the wind blowing pretty fierce. The top bunks get pretty hot, granted I only have an 8' ceiling, but I do have a small 12 volt ceiling fan.

I understand the concerns for co2 and do use a co2 detector. I don't really notice an odor but then again I don't run it when I'm not there. Those heaters are approved for mobile home use and garages. You could try to find an older vented space heater, a Warm Morning model for example, also do not use electricity, are not very energy efficient either.

The blower motor needs to run for the furnace to work and in cold weather the batteries will need to stay charged. Most solar panels only put out a few amps and my concern would be keeping up with the power demand for the blower motor. I have used a travel trailer in cold weather and the insulation was not good meaning the blower ran almost continuously in sub zero weather. So there are a lot of variables including the size of solar panels, how cold it gets and stays and how well your place is insulated.

I bought a pro con ventless heater. But, talking to the gas company, they said that there will be a build up of Co2, and smell of propane, along with it being illegal and insurance possibly dropping me if they find out.

That was my plan, until I learned that info. That is where I was thinking of an RV forced air furnace.